The invention relates to a method and an apparatus for performing a feedback free ABS control.
Generally, the use of so-called plunger systems, which are capable of achieving ABS operation without perceptible feedback in the brake pedal of the master brake cylinder, is known in various forms, for instance from Bosch Technische Berichte [Technical Reports] 7 (1980), page 76, FIG. 14b, where a plunger operating pump with its own supply is disclosed that can be selectively used to jointly supply a brake booster as well.
The basic function of a hydraulic control unit for feedback-free ABS operation using plunger-pistons is known, for instance from the article entitled "Mehr Sicherheit beim Bremsen" [Increased Safety When Braking] from the periodical Fluid, January 1984, page 10. In the customary manner, this known hydraulic control system for an anti-skid braking system includes wheel sensors, a control and regulation electrode, and the hydraulic control unit. The hydraulic control unit provides a check valve in the connecting line between the pedal-actuated master brake cylinder and the various wheel brake cylinders, along with a plunger-piston connected parallel to and downstream of the check valve, which upon triggering in the ABS mode diverts a volume of pressure fluid from the line and from the connected wheel brake cylinders, and as a result closes the check valve toward the master brake cylinder and then independently thereof realizes the ABS function as needed during operation. The electronic control and regulation system assures that the pressure that takes the various road conditions into account is established by means of predetermined pressure gradients in the brake system. If the pedal force at the master brake cylinder is lessened, the check valve can open again, so that the line between it and the connected wheel brake cylinders becomes free again.
In the same way, it is known to dispose controlled check valves between the master brake cylinder and to combine a wheel brake with a plunger cylinder (German Offenlegungsschrift 2 045 689); the actuation of the plunger cylinder is done via an auxiliary pressure by means of a magnetic valve.